Deformation image reproduction process utilizing a voltage threshold reducing surfactant



P w A 2 a n m, m m a w. L. GOFFE DEFORMATION IMAGE REPRODUCTION PROCESSUTILIZING A VOLTAGE THRESHOLD REDUCING SURFACTANT Filed Nov. 29, 1963May 16, 1967 WILLI KYA L TE CSFFE w Q&

FIG. 5

A 7' TORNE Y United States Patent 3,320,060 DEFCRMATEQN IMAGEREHEGDUCTHGN PRUC- ESS UTILHZING A VCLTAGE THRESHOLD RE- DUCINGSURFACTANT William L. Golfe, Webster, N .Y., assignor to XeroxCorporation, Rochester, N.Y., a corporation of New York Filed Nov. 29,1963, Ser. No. 326,831 22 Claims. (Cl. 96--1.1)

This invention relates to deformation imaging and in particular to frostdeformation.

The usual ways of electrostatically deforming a deformable surface inaccordance with an image pattern have required some means of depositingelectrostatic charge selectively. The two most common ways of doing thishave been to use a photo-conductive insulating layer in order toselectively control the movement of electrical charges in accordancewith a light pattern, or else to use a direct means of selectivelydepositing the electric charge as with an electron beam or by chargingthrough a stencil.

In accordance with the present invention, it has been discovered thatselectively treating a deformable surface with appropriate surfactantswill produce selective deformation in accordance with the deposition ofsuch agents when the deformable material is uniformly electrostaticallycharged. This has been found particularly true in the case of frostdeformation of the type disclosed in US. patent application, Ser. No.193,277, filed May 8, 1962. As described in that application and as usedherein, the term frost generally describes a random minute wrinklingproduced by electrostatic charge on a soft insulating thermoplasticlayer. Thus, it is an object of the present invention to define a methodof deformation imaging in which the latent image comprises a surfactant.

It is an additional object to define a vapor thermographic process ofdeformation imaging.

It is an additional object to define method and means for forming adeformation image from a developed, transferred, xerographic image.

It is still a further object to define means for forming a frost imageby selective deposition of a surfactant. Further objects and features ofthe invention will become apparent while reading the followingdescription in connection with the drawings wherein:

FIG. 1 is a diagrammatic illustration of forming a latent image with asurfactant and a stencil;

FIG. 2 is a diagrammatic illustration of development of an image made inaccordance with the present invention;

FIG. 3 is a diagrammatic illustration showing a selective deposition ofa surfactant by vapor thermograph;

FIG. 4 is a diagrammatic illustration of fingerprinting in accordancewith the present invention;

FIG. 5 is a diagrammatic illustration of means for continuously formingimages in accordance with the present invention using vapor thermograph;and,

FIG. 6 is a diagrammatic illustration of means to form images inaccordance with the present invention using xerography.

A frostable material generally exhibits a threshold, related to bothelectrostatic charge and temperature, at which frost deformation willbegin to develop. This threshold, it has been found, can be made to varyby contamination of the surface by materials having the characteristicsof surfactants. As used herein, the term surfactant denotes a substancefor modifying the properties of a liquid medium at an interface byraising or lowering interfacial tension.

It was found, for example, that a thin film of Dow- 3,32%,966 PatentedMay 16, l 967 Corning D0200 silicone oil of 50 centistoke viscosity willdrop the voltage threshold for frost development by 50%. Accordingly,the present invention concerns this effect and various means ofutilizing it to form image-s. Thus, in FIG. 1, image-forming member 10is illustrated as comprising conductive substrate 11 such as aluminum orother metal and deformable material 12 coated over substrate 11 incontact with the conductive surface. Substrate 11 can also be atransparent glass or plastic with a conductive coating eithertransparent, such as made with stannic oxide, or opaque as with anopaque thickness of evaporated metal. Suitable deformable materials are:

TAB LE I Trade N ame Chemical Type Manufacturer (1) PiccotexPennsylvania Industrial Chemicals (2) Piccolyte Do. (3) Stayoelite 5Hercules Power Co. (4) Staybelite 10 Do. (5) Piecoumaron CoumaronePennsylvania gndustrial Chemicals 0. (6) Piccolastic D150". Styrene Do.

(7) Piccoflex A Polyvinyl chlorlde The thickness of the substrate is notimportant, but the resistivity of the substrate, at least that portionof it adjacent to the deformable material, must be less than 10 ohm-cm.and is preferably less than 10 ohm-cm. The deformable material shouldpreferably have a thickness between /2 micron to 6 microns. Thinnerlayers give better resolution While thicker layers enable greater imagedensity. One means of forming an image on this member is illustrated inFIG. 1 as positioning a stencil 13 against the surface of deformablematerial 12 and then applying a surfactant through the stencil. Anyconventional type of stencil that will permit passage of the surfactantin the image areas may be used. The surfactant may be applied by meansof an atomizer 15 as illustrated, or by means of a brush roller or anyother device capable of applying the surface active material through thestencil. In one preferred embodiment, for example, deformable material12 is a 2 micron layer of glyceral ester of abietic acid in which theabietic acid has been approximately 50% hydrogenated. This deformablematerial is sold under the name Staybelite 10 as listed above. Thedeformable material is thinned with a volatile solvent such as methylethyl ketone to a suitable coating consistency and then the substrate isdip coated at a speed to give the desired coating thickness. Thesurfactant for lowering the voltage threshold for frosting must readilywet the deformable material and should have a lower viscosity so as tolower the surface tension at the interface between the deformablematerial and the surfactant. An exemplary surfactant for use withStaybel-ite ester 10 is dimethyl polysiloxane (Dow-Corning DCZOOsilicone oil) having a viscosity of 50 centistokes. The stencil is thenremoved from the image forming member and the deformation image isdeveloped as illustrated in FIG. 2.

Particularly in a process such as that described above in Which thesurfactant is applied mechanically or by a pray, the thickness of thesurfactant layer may raise roblems. A low viscosity material such as 50centistoke ilicone oil will flow readily and tend to fill the depresionsof the deformation image. While the image is still isible with thedepressions completely filled in, the conrast is greatly reduced sincethe refractive index differnce between the deformable material and thesurfactant not as great as between the surfactant and air. Thus, t ispreferable that the surfactant be applied in layers hat are thinner thanthe deformation depth of the frost mages, so that the surfactant surfacefollows the deformaions. Since the deformation depth is limited by thehickness of the deformable material, the surfactant layer hould be nothicker than one half micron and substanially thinner than the thicknessof the deformable maerial. Alternatively, a thick surfactant can bewashed if after forming the frost image.

FIG. 2 illustrates image forming member positioned vith its substrateagainst heating means 16. While this [eating means is illustrated as ahot-plate type of device :ontaining an electrical resistance heatingelement, other neans for heating image forming member 10 to frostemperature can be used. Thus, the entire member may e placed in an ovenor heat may be directed at the deormable material by the use of heatlamps or the like. A :orona discharge device 17 is used to apply anelectrotatic charge in the range of 50 volts to 1200 volts to theleformable material before or during heating by heating neans 16. Therequired minimum voltage is determined )y the frost threshold which inturn differs depending on he particular deformable material and on thesurfactant. lhirty volts is about as low as the threshold can be broughtwith practical materials. Thus, the charge voltage must :xceed thirtyvolts. The higher the charge voltage, the more linear the developmentcurve becomes until short :ircuit problems start to occur usually inexcess of 1200 volts. Heat is applied until frosting occurs in the imageareas. This will generally be when the heat has softened :he deformablematerial to a viscosity between about 10 and 10 poises.

FIG. 3 and FIG. 4 illustrate other methods of applying in image surfaceactive material to imaging member 10. Thus, in FIG. 3, an original imageto be reproduced is :hinly coated with volatile surfactant 19 over itsimage nearing surface. The original 18 is then positioned inface-to-face contact with deformable material 12. An infrared source 20is then directed at the back of original 18. It should be understoodthat for this purpose, the Image areas of original 18 mustpreferentially absorb .nfrared light in relation to the non-image areasand that :he supporting substrate of the original must be transpar- :ntor translucent to infrared energy.

Infrared energy from source 2%) passes through the back 3f original 18and is preferentially absorbed in the image areas causing selectiveheating of the image areas. This ;e1ective heating vaporizes some of thesurface active ma- :erial from the face of original 18 so that ittransfers to deformable material 12 in image configuration. The Jriginalis then separated from imaging member 10 and deformation image may bedeveloped as described in rela- :ion to FIG. 2.

The present invention offers a simple and unique means forfingerprinting. One of the advantages of this means 3f fingerprinting isthat it is readily adapted to producing projectable fingerprints. Thus,as illustrated in FIG. 4, in image forming member 10 similar to imageforming rnember 10 of FIG. 1 and FIG. 3 is illustrated with atransparent substrate. The substrate is depicted as glass layer 21coated with a transparent conductive layer such as stannic oxide coating22. A layer of deformable ma- :erial 12 is coated over layer 22. To makea latent fingerprint image on the layer of deformable material 12, thesubjects finger 23 is merely rolled lightly against the de- Eormablematerial in the way customarily used for ink fingerprinting, but withoutthe use of ink. Human fingers normally have enough skin oil to providethe necessary surface active agent for operation in accordance with thepresent invention.

In fact, it has even been found desirable to clean the subjects handsbefore fingerprinting to avoid contaminating the deformable surface witha multitude of foreign materials which will tend to obscure thefingerprints rather than to help develop them. As long as the subjectshands are not obviously dirty, wiping the finger with facial tissuesbefore fingerprinting is sufficient to insure good fingerprints. As withthe embodiments of FIGURES l and 3, development is produced byelectrostatic charging and heating as described in connection with FIG.2. The frost image of the fingerprint thus produced can be readilyprojected by light transmitted through imaging member 10 and willreadily produce a good high contrast image particularly if a Schlierentype optical system is used. If the substrate used in any of FIGURES 1,3, and 4 is highly reflective, such as with polished aluminum, a Proxiprojection system can be used for projecting the images. Such a systemis described in Photographic Science and Engineering, March-April 1961at pages 87 to 92. A continuous image forming system is illustrated inFIG. 5 for forming micro images by the inventive process. Imaging member25 in accordance with this embodiment is a flexible web having a supportlayer in a substrate of a dimensionally stable flexible material such aspolyethylene terepht-halate cellulose acetate or other similar plasticmaterial. This substrate may itself be conductive as by the inclusion ofa conductivity agent such as for example, stannic chloride just assuitably a conductive coating of evaporated metal or metallic oxide maybe applied to the surface of the plastic substrate to provide thedesired electrical conductivity. A layer of deformable material is thenapplied over the substrate and web 25 is positioned for support throughan exposure station 26 by means of supply reel 27 and takeup reel 28driven by motor 30.

An exposure station 26, a lens system 31 focuses an intense reduced sizeimage of an original 32 on the deformable surface of web 25. While othermeans of projected original image can be used, the illustratedembodiment depicts the means of projecting the light image as one usinga light reflected from the original. Light source 33 illuminatesoriginal 32 and the light passes through a prism 36. Prism 36 serves thepurpose of a high efiiciency mirrorreversing the image sense anddirecting the projected image through lens system 31 to Web 25, toenable continuous image forming. A conventional slit 37 is used in theoptical system. In operation, the deformable surface of web 25 isuniformly coated with a surfactant by roller 38 to which the surfactantis supplied by fountain device 40. The surfactant for this purpose isdesirably a highly volatile material such as fluorocarbon, for example,FC43 fluorocarbon available from Minnesota Mining and Manufacturing. Theimage at exposure station 26 evaporates the surfactant in the backgroundareas so that when the web is then electrostatically charged at chargingstation 41 and softened at soften-ing station 42, depicted as a heatingoven, the deformable surface of web 25 frosts in the image areas. Web 25is then reeled on reel 28 and stored for future use, while the image maybe projected off the web immediately as desired. Since heating oven 42vaporizes and removes most of the remaining surface active agent and thefrost images formed on web 25 can be erased at any time by heating wellabove frost temperature until erasure is accomplished, web 25 may bereused repeatedly. Apparatus using xerographic method of applying thesurface active agent is illustrated in FIG. 6. This apparatus comprisesxerographic drum with conventional charging station 51, exposure station52, development station 53, and transfer station positioned around itrespectively in the direction of rotation. In operation, the Xerographicdrum is charged at charging station 51 exposed to an original image 56exposure station 52 and is developed in developing station 53. Forpurposes of the present invention, developing station 55 suitablycomprises a spray or liquid vapor developing 4. A method of deforming aninsulating thermoplastic layer according to claim 1 in which saidsurfactant is applied by a roller.

5. A vapor thermographic reproducing process commeans such as described,for example, in Carlson Patent 5 prising, in sequence, the steps of:

No. 2,551,582. This developing means is used to apply a colorlesssurface active agent to the latent electrostatic image on drum 50. Attransfer station 55 a Web 62 of material having a deformable surfacelayer is supported in contact with the surface of the drum by supplyreel 57, support rollers 58 and takeup reel 60. Xerographic drum 50 andtakeup reel 60 are driven synchronously by motor 61. Web 62 can comprisea paper substrate with .a reflective conductive coating, such as anevaporated or laminated metallic coating. The reflective surface of thepaper is coated with a layer of deformable material and the layer ofdeformable material is passed in contact with the xerographic drum Whilea transfer charge is applied to the back of the web by a charging device63. This transfers the image of the surface active material to thedeformable layer. Deformable layer is then electrostatically charged asby double corona charging device 65 followed by heating at a heatingdeveloping station 66. The frost image is developed on a web of the typedescribed using a refractively coated paper backing. Projection of theimage is readily obtained using a Proxy system as previously described.However, it is also possible in the embodiment of FIG. 6 to use acompletely transparent web material such as described in connection withFIG. 5, for example, and view the frost image by transmitted rather thanreflected light.

While the disclosed embodiments have been directed to processes in whichthe surfactant lowers the voltage threshold for frost surfactants canalso be used to raise the voltage threshold for frost. Thus, forexample, dimethyl polysiloxane, having a viscosity of 2,500,000centistokes deposited on Staybelite 10 will raise the surface tension atthe interface and increase the voltage threshold for frost. PhotographicGelatin (as defined in The Condensed Chemical Dictionary, FourthEdition, 1950, Reinhold Publishing Corporation) also raises theinterfacial tension and thus the frost threshold.

While the present invention has been described as carrying out specificembodiments thereof, there is no desire to be limited thereby. Othersystems for using the present invention are readily thought of as forexample, the latent image of surface active material may be formed by aspot scanning system in which the layer of deformable material isuniformly coated with a volatile surface active agent, and an intensemodulated spot of light is used to scan the deformable surface toselectively evaporate the surface active agent. Accordingly, it isintended to cover the invention broadly within the scope of the appendedclaims.

What I claim is:

1. A method of deforming an insulating thermoplastic layer in accordancewith a stencil pattern comprising, in sequence, the steps of:

(a) positioning a stencil of permeable and non-permeable areas incontact with said thermoplastic layer;

(b) applying a surfactant for said thermoplastic layer through saidpermeable areas;

(c) removing said stencil;

(d) electrostatically charging said thermoplastic layer and heating saidthermoplastic layer until it reaches a viscosity between 10 and 10poises whereupon deformation occurs in the stencil pattern.

2. A method of producing a deformation image according to claim 1 inwhich said surfactant is dimethyl polysiloxane.

3. A method of deforming an insulating thermoplastic layer according toclaim 1 in which said surfactant is applied as an atomized spray.

(a) placing an original having an image surface carrying a volatilesurfactant with said image surface in contact with a layer of deformablethermoplastic material;

(b) heating said original so that said volatile surfactant transfers toareas of said layer in contact With heated areas of said original;

(c) removing said original from said layer;

(d) electrostatically charging said layer; and,

(e) softening said layer until surfactant-bearing surface areas deforminto minute random wrinkles;

(f) hardening said layer.

6. A vapor thermographic reproducing process according to claim 5wherein said volatile surfactant is carried in the image areas only andsaid heating of said original is uniform.

7. A vapor therrnographic reproducing process according to claim 5wherein said volatile surfactant is carried uniformly over the surfaceof said original and said heating of said original is selective to theimage areas.

8. A vapor thermographic reproducing process according to claim 7wherein said heating is by infrared light.

9. An inkless fingerprinting process comprising, in sequence, the stepsof:

(a) transferring the natural skin oils of a subjects fingers to a layerof deformable thermoplastic material;

(b) electrostatically charging said layer; and,

(c) softening said layer until its surface deforms into an image patternof the fingerprint;

(d) hardening said layer bearing said deformation image pattern.

10. A process for making microimage comprising:

(a) applying a volatile surfactant uniformly to the surface of athermoplastic layer;

(b) intensely illuminating an original to be reproduced;

(c) focusing the light image produced by illuminating said original inreduced size onto said layer so as to selectively evaporate saidsurfactant from said layer;

(d) electrostatically charging said layers; and,

(e) softening said layer so that it deforms in minute random wrinkles inthe areas where said light image did not evaporate said surfactant.

11. A process for forming a deformation image in a layer ofthermoplastic material, comprising in sequence, the steps of:

(a) xerographically forming a latent electrostatic image on the surfaceof a xerographic drum;

(b) developing said latent electrostatic image with a surfactant for alayer of deformable thermoplastic material;

(c) transferring said surfactant to said layer of deformablethermoplastic material;

(d) charging said layer of deformable thermoplastic material; and,

(e) softening said layer of deformable thermoplastic material until itdeforms into minute random wrinkling in the areas of transferredsurfactant.

12. A method of producing a pattern upon an insulating thermoplasticlayer, comprising in sequence the steps of:

(a) positioning a pattern-bearing stencil in contact with saidthermoplastic layer;

(b) applying a surfactant to said thermoplastic layer through saidstencil;

(c) removing said stencil;

(d) electrostaticaliy charging said thermoplastic layer;

7 (e) softening said thermoplastic layer until surfactant-bearingsurface areas deform into randomly oriented ridges and valleys; (f)hardening said thermoplastic layer. 13. A method of producing a patternupon an insulatg thermoplastic layer, comprising in sequence the steps(a) applying a surfactant to a thermoplastic layer in a desired pattern;

(b) electrostatically charging said thermoplastic layer;

(c) softening said thermoplastic layer until surfactantbearing surfaceareas deform into randomly oriented ridges and valleys; and,

(d) hardening said thermoplastic layer.

14. A method of producing a pattern upon an insulatlg thermoplasticlayer comprising in sequence the steps (a) positioning a pattern bearingstencil in contact with said thermoplastic layer;

(b) applying a surfactant for said thermoplastic layer through saidstencil;

(c) removing said stencil;

(d) electrostatically charging said thermoplastic layer;

(e) softening said thermoplastic layer until a deformation pattern formsthereon corresponding to the pattern of said stencil; and,

(f) hardening said thermoplastic layer.

15. A vapor thermographic reproducing process comprising in sequence thesteps of:

(a) placing an original having an image surface carrying a volatilesurfactant with said image surface in contact with a layer of deformablethermoplastic material;

(b) heating said original so that said volatile surfactant transfers toareas of said thermoplastic layer in contact with heated areas of saidoriginal;

(c) removing said original from said layer;

(d) electrostatically charging said layer;

(e) softening said thermoplastic layer until surfactant- 'bearing areasdeform into randomly oriented alternating ridges and valleys ofcontinually variable average depth; and;-..

(f) hardening said thermoplastic layer.

16. A vapor thermographic reproducing process acording to claim whereinsaid volatile surfactant is arried in the image areas only and saidheating of said triginal is uniform.

17. A vapor thermographic reproducing process ac- :ording to claim 15wherein said volatile surfactant is :arried uniformly over the surfaceof said original and aid heating of said original is selective to theimage areas.

18. A process for forming a frost deformationpattern :omprising:

(b) softening said thermoplastic layer until areas hearing bothelectrical charge and surfactant deform into randomly oriented ridgesand valleys; and then,

(c) hardening said thermoplastic layer.

19. process for forming a frost deformation pattern comprising:

(a) applying electrical charge on a first surface of a frostable,insulating, thermoplastic layer coated on at least a portion of saidfirst surface with a thin layer of a voltage threshold reducingsurfactant for said thermoplastic;

(b) softening said thermoplastic layer until areas hearing bothelectrical charge and surfactant deform into randomly oriented ridgesand valleys; and then,

(c) hardening said thermoplastic layer.

20. A recording member comprising:

(a) a frostable, insulating thermoplastic layer and;

(b) a thin layer of a voltage threshold modifying surfactant on at leasta portion of a surface of said thermoplastic layer.

21. A recording member according to claim 20 in which said surfactantlayer has a thickness of less than about 0.5 micron.

22. A method for modifying the voltage threshold required to form afrost deformation pattern on a frostable insulating thermoplastic,comprising depositing a layer of a surfactant for said thermoplastic onthe surface of said thermoplastic, said surfactant layer having athickness of less than about 0.5 micron.

References Cited by the Examiner UNITED STATES PATENTS 2,020,376 11/1935Rich 962.7 2,857,271 10/1958 Sugarman 961 2,896,507 7/1959 Mast et al88--61 3,055,006 9/1962 Dreyfoos et a1. 961 X 3,079,253 2/1963 Greig 9613,081,165 3/1963 Ebert 96-1 3,258,336 6/1966 Ewing 961.1

FORElGN PATENTS SHO-37-4484- 3/1960 Japan.

OTHER REFERENCES Gundlach et al.: A Cyclic Xerographic Method Based onFrost Deformation,.Phot. Sci. and Eng. vol. 7, No. 1, January 1963, pp.1419.

Olin: Photoplastic Recording, Industrial and Engineering Chemistry, vol.55, No. 6, June 1963, pp. 11 and 12. Claus: Advances in Xerography,Phot. Sci. and Eng,

' vol. 7, No. 1, January 1963, pp. 5-14.

NORMAN G. TORCHIN, Primary Examiner. J. T. BROWN, Examiner.

A. LIBERMAN, C. E. VAN HORN,

Assistant Examiners.

13. A METHOD OF PRODUCING A PATTERN UPON AN INSULATING THERMOPLASTICLAYER, COMPRISING IN SEQUENCE THE STEPS OF: (A) APPLYING A SURFACTANT TOA THERMOPLASTIC LAYER IN A DESIRED PATTERN; (B) ELECTROSTATICALLYCHARGING SAID THERMOPLASTIC LAYER; (C) SOFTENING SAID THERMOPLASTICLAYER UNTIL SURFACTANTBEARING SURFACE AREAS DEFORM INTO RANDOMLYORIENTED RIDGES AND VALLEYS; AND, (D) HARDENING SAID THERMOPLASTICLAYER.
 22. A METHOD FOR MODIFYING THE VOLTAGE THRESHOLD REQUIRED TO FORMA FROST DEFORMATION PATTERN ON A FROSTABLE INSULATING THERMOPLASTIC,COMPRISING DEPOSITING A LAYER OF A SURFACTANT FOR SAID THERMOPLASTIC ONTHE SURFACE OF SAID THERMOPLASTIC, SAID SURFACTANT LAYER HAVING ATHICKNESS OF LESS THAN ABOUT 0.5 MICRON.